Source : Free On-Line Dictionary of Computing

SCSI ID
     
         The unique address of a {SCSI} device.  SCSI IDs
        range from 0 to 7 for 8-bit SCSI systems, 0 to 15 for 16-bit
        and 0 to 31 for 32-bit systems.  The {SCSI adaptor} is
        usually assigned ID 7.  A device's SCSI ID is often set by
        switches on the device.
     
        (1999-09-01)